The present invention relates to chemical analysis and cleansing of liquid streams and more particularly to liquid chromatography and wastewater treatment.
At present, liquid-phase chemical separations are usually performed in “columns” prepared by the packing of metal tubes with spherical beads that are composed of either silica or polystyrene and have diameters of 3 to 50 μm. The more or less inert beads provide solid supports that are chemically modified to produce a surface having targeted chemical characteristics. For example, in performing reversed-phase liquid chromatography, long carbon chains (C-18) can be affixed to the surfaces of the beads so as to produce a hydrophobic surface for the separation of non-polar organics. In some systems, beads can include particular surface polymers upon formation, precluding the necessity of post-formation modification of the materials.
Effective separations require dense packing of the beads into these columns to avoid dead-volume, which is any location within the column where turbulence can occur and interactions between molecules in the liquid and the surfaces of the beads are minimal. As a consequence of dense packing, high driving pressures (e.g., 2,000 to 5,000 psi) are required to overcome the backpressures that otherwise would prevent the liquid phase from moving through the densely packed columns.
Alternatively, highly porous “monoliths” are formed within the columns to generate high surface areas for interaction with the species that flow through the columns. Here, the high backpressures and a limited set of stationary phase chemistries can be restrictive. In the case of so-called “prep-scale” separations, the capital costs associated with producing large volume columns and the demands on the system hydraulics (i.e. pumps) are very high.